package demo;


public class MyLinkedList {
    static class ListNode {
        public int val;
        public ListNode prev;//前驱
        public ListNode next;//后继

        public ListNode(int val) {
            this.val = val;
        }
    }

        public ListNode head;
        public ListNode last;

        //头插法
        public void addFirst(int data) {
            ListNode node = new ListNode(data);
            if (head == null) {
                head = node;
                last = node;
            } else {
                node.next = head;
                head.prev = node;
                head = node;
            }

        }

        //尾插法 O(1)
        public void addLast(int data) {
            ListNode node  = new ListNode(data);
            if(head == null){
                head = node;
                last = node;
            }else{
                last.next = node;
                node.prev = last;
                last = node;
            }

        }

        //任意位置插入,第一个数据节点为0号下标
        public void addIndex(int index, int data) {
            if(index <0 || index >size()){
                throw new ListIndexOutOfException();
            }
            if(index == 0){
                addFirst(data);
                return;
            }
            if(index == size()){
                addLast(data);
                return;
            }
            ListNode cur = findIndex(index);
            ListNode node = new ListNode(data);
            node.next = cur;
            cur.prev.next = node;
            node.prev = cur.prev;
            cur.prev = node;


        }
        private ListNode findIndex(int index){
            ListNode cur = head;
            while(index!=0){
                cur = cur.next;
                index--;
            }
            return cur;
        }

        //查找是否包含关键字key是否在单链表当中
        public boolean contains(int key) {
            ListNode cur = head;
            while (cur != null) {
                if (cur.val == key) {
                    return true;
                }
                cur = cur.next;
            }
            return false;
        }

        //删除第一次出现关键字为key的节点
        public void remove(int key) {
            ListNode cur = head;
            while(cur!=null){
                if(cur.val == key){
                    //1. 删除头结点
                    if(cur == head){
                        head = head.next;
                        //只有一个节点
                        //head是空不用处理前驱
                        if(head != null){
                            head.prev = null;
                        }

                    }else{
                        cur.prev.next = cur.next;
                        if (cur.next != null){
                            //2. 中间
                            cur.next.prev = cur.prev;
                        }else{
                            //3. 尾巴
                            last = last.prev;
                        }
                    }
                    return;
                }
                cur = cur.next;
            }
        }

        //删除所有值为key的节点
        public void removeAllKey(int key) {
            ListNode cur = head;
            while(cur!=null){
                if(cur.val == key){
                    //1. 删除头结点
                    if(cur == head){
                        head = head.next;
                        //只有一个节点
                        //head是空不用处理前驱
                        if(head != null){
                            head.prev = null;
                        }

                    }else{
                        cur.prev.next = cur.next;
                        if (cur.next != null){
                            //2. 中间
                            cur.next.prev = cur.prev;
                        }else{
                            //3. 尾巴
                            last = last.prev;
                        }
                    }

                }
                cur = cur.next;
            }
        }


        public int size() {
            int len = 0;
            ListNode cur = head;
            while (cur != null) {
                len++;
                cur = cur.next;
            }
            return len;
        }

        public void display() {
            ListNode cur = head;
            while (cur != null) {
                System.out.print(cur.val + " ");
                cur = cur.next;
            }
            System.out.println();
        }

        public void clear() {
            //val域如果是引用类型也得置空
            ListNode cur = head;
            while(cur!=null){
                ListNode curNext = cur.next;
                cur.prev = null;
                cur.next = null;
                cur = curNext;
            }
            head = null;
            last = null;
        }



}


